Beam antenna system



Feb. 13, 1951 B. P. BROWN, JR

BEAM ANTENNA SYSTEM Filed May 4, 1945 TJUUUUUUU Fig.3.

TRANSM/TTER F70 MTING JOIN 7' Inventor Burton P BToyvn Jn,

His Attornev.

fatented Feb. '13, 1951 I "can PATENT BEAM; ANTENNA. SYSTEM BurtonBrown, In, Scoti'aQNfY}, assignor'ftq IGeneraI Electric flompany, -'a corporation :01

New zYork ApplicationMay 4,1943;.Seria1No..485,i6'0.1

'f lllain'ls. 7 55 (01. 250- 3355 1 Thisiinvention *reiatesito' antenna isystemsiand more-imarticularly to'antenna systems adapted for radiating 451121111 13! directive 'beams 'of radio frequency energy.

"Systems have been propose'din which periodic pulses. of short wave oscillations .have'beenrad'iatte'dfintov space arfd'an echo of each pulse has been recei'vedi'n the period priorl-to'the next sucflector in order .to rotate the .beam about the surfaceiof. a cone, the, of whichisthe. axis ofilthe reflector. The. radiating system. including. theirefiector :is arranged to be oriented both in .eievationandin azimuth by suitable mechanical. -meimsiso that the x-axisiof the paraboloid canbe directed .atia remote objectsuch. as aitargetrand maintained so oriented.

,..s1'1ch :systeins have been generally described and claimed in application. Serial. N0.,;4S2,.403 ito Donald Norgaard, ,filedJApril. 9, l943 now Patent. 2,455,265,. gran-ted. November-.30 ,11948, and application Serial No..414,12'6,.of. Sidney-Godet, filed. Qctober 1942;..now- Patent -2A12,,612, =granted DecemherlG, -.1946, both of whichareassi'gneld tothe same-assigneeias the present invention.

. is an object of .my invention .to provide-a new and improvedantenna. system for such systemsxofcommunication.

-It.; is;.-a-nother=obj;ect of my invention toproaide asearch antenna for such-a system-which is! simple.- inzform, easy -.of manufactureand as:- sembly, relatively inexpensive, and so arranged that .theiradiating partsiare :not subject to any appreciable centrifugal; force.

.Tfheiieatures .ofmy'in-vention which. I believe to'he novel are set forth .withparticularity .in the -appended claims. My invention itself, yboth as to its organization and manner. oiv operation. tcgether with further objects and advantages therco=;may .bestLbe: understood by reference to the :following description taken in connection w-ithlthe-iaccompanying drawing in which.F.'ig...1 isge partialplan view or an. antenna. system emhodyin-g theprinciplesof my invention; Fig. 2 is agsectionaiiside elevationalwiew of .the. .appa

ratus shown in Fig. 1; and Fig. 3 is an eniarged view" of theantenna element 'and associateid' re- Hector elementshowrr irr' Figsxi andZ'.

in the accompanying drawing there is shown an :antenna system comprising a paraboloid re- I .fiectorlflyan" antenna-member H, and-a reflectorv member f 2. The antenna member I' I; is ortne dipole"type-'including colinear elements [3 and f4. Thedi'poleis locatedat or-neartheiocus of the gparaboioid reflector and'the axis of thereflector i=0 passesthroughthe-dipole at-ornear themfdpoint thereof. Whil there is illustrated a reiiectoreiement ['2 it willf'be understood "that theelement lF-Z-mawbe omitted, if desired. However, '"thereiiecton element ['2 "reflects energy "ra diated outwardly from the antenna element; H

" into the p-araboloid'reiiector i0 sothatasharper beam results when the reflector element [2 "is used,

"Means is'provid'ed for exciting the antenna element. H. "Thismeans comprises-a source Of sigh mil 'energy which"may"'be considered to "be in-'- cludedin the "boxindicated bynumeral f5, an open; transmission'line i i B-and a concentric transmissionlline [1, the latter comprising an; inner conductor [8, representedby lthedotted lines in Fig.2, "andran'outer cylindrical conductor ortu'b'e; [9 "through which the inner conductor extends; The inner conductor fextends "aiong "the 'axis or thetparaboloid.

"The "source ofxsignai energy .or transmitter contained within the box l5 produces .pulses'of oscillations of high frequency energy .ian'di sup plies them to the transmission line 16. pulses .are .trans'f'erredl'to the concentric transmissioniine section IT through a, suitabl type of rotating jointgindicated by the numeral 20,

Thgantenna, array comprising the elements H and 12 also receives echo .pulses and supplies themtoatsditablapdlse.receiver which may, also of the reflector and for rotating. the; antenna..as

senibly so. that=a rotatingl beam will. beproj'ecteii. In I the. illustrativefformnf. my invention,.'t hedipole is'tilte'd, that is, disposed at an angle of other.

than with respect to theaxisof theparabo 1cm reflector. This arrangement causes-[the projecting beam .tohavean. angle ofjaf'ew degrees with respect. .to the, paraboloid, axis iThe' beamj.

shift may be increased .iurther'. by .unbalancin'g. the. currentsin the antenna elementsv l3 an'd'ldf.

Itiis. .well. known that in order Lto have balanced}.

current inthe arms'or; elements of a dipole \izhexij those e as .s ee e tre t-rea a cylinder of approximately one-quarter wave length may be attached to the end of a concentric transmission line used for exciting the dipole, the cylinder being concentrically disposed with and surrounding the transmission line, open at the radiating end of the line, and attached to the outer conductor of the-line at the other end. In the form of my invention described herein no such line balancing arrangement is employed so that the means for conducting the may be made of different lengths as shown in the drawing.

. .In-order to permit the determination of the elevation and azimuth of the object from which echoes are received, it is desirable to rotate t he displaced pattern about the axis of the paraboloid reflector. For this purpose there is provided a suitable motor 2| receiving electrical energy from a suitable source, not shown,'and carriedbythe base plate 36 attached to the paraboloid reflector in any suitable manner. The motor is operatively J connected to the outer conductor I9 through suitable gears 22 and 23 carried by the shaft of the motor and the outer conductor or tube I9 re spectively. The rotation producing meansand the transmission line H are mounted as shown at the center of the paraboloid reflector. Because of the mechanical couple resulting from the uh; balanced disposition of. the dipole, there results a tendency of the parts of the antenna assembly to whip during rotation. In order to minimize the efiects of centrifugal force, the transmission line section I! issupport'ed as close as practicable to the dipole. For this purpose there has been provided a conically shaped support 25 located at the center of the paraboloid reflector and at-. tached to the base 36 at the large end. Suitable bearing means 26 is provided 'at the small end'of the cone. If desired, "a bearing may also be providedfwhere transmissionline I1 passes through the supporting structure. At any rate,- the .itran's- In order to obtain intelligence which maybe employed to cause" the antenna system, including the paraboloid reflectorgto followthe target or', source of echo, there has been shown a two-phase alternator .28 suitably carried by the paraboloid 19,, of course, is electrically insulative.

1 able manner as by means of the threaded for securing the element I 3 to the outer conductor in such a manner as to lend support to the inner conductor and to maintain that conductor fixed with respect to the outer conductor during rotation of the apparatus thereby minimizing the effects of centrifugal force on the inner conductor and the reflecting member I2. The means connecting the elements I3 and the outer conductor In the form of my invention illustrated herein, this purposeis accomplished by providing a stud 30 having a threaded laterally extending portion 3| adapted to engage thethreads of a suitably tapped bore in the end of the arm I3. An insulating .member32 is retained at the opening in the outer member I9 between the stud 30 and the end of the arm ,l3. -,For example, the cage of the member 32 maybe suitably secured to a metal washer 32a and the outer edge of the member or washer 3211 may be engaged'bya'fla'nged member 33 having in: ternal threads engaging suitable threads in the outer surface of the washer 32a. The inner end of the stud 30 is securely fastened to the inner conductor I8"as by means of a suitably threaded fastening member 34 passing through a suitable opening in the conductor I8 into suitable threaded engagement with the bore in the stud30. The arm I3 is shown bent at the inner end thereof in, order to approach the inner. conductorat right angles thereto for convenience of assembly. With this arrangement, the stud may be fastened in p05 sition, the insulative washer applied over the lateral portion 3! of the stud 30 and the flanged member 33 fastened in place. The arm I3may thenbe screwed onto the lateral portion 3I of the stud. The reflector member I2 may be secured to the end of the inner conductor I8 in any suit ingmember 35. 1 I The above described means for supporting the antenna system and associated parts is not my in'- vention but is disclosed and claimed in 'a"co -t pending application of C. L. Rouault, application Serial No. 483,555,'filed April 19, 1943, now Patent 2,446,436, granted August 3, 1948, 'and'as-j signed to' the same assignee as the present inven tion. u '5. j A system embodying the above-principle has been constructed for operation at approximately, 40 Q megacycles. The dipole was tilted 13 with respect to a plane perpendicular to the ajxisQof the paraboloid reflector. The antenna members II and I2 were each approximately enemas-wave length long and spaced apart at their centersap-f proximately one-quarter wave length. The '-re flector element was one inch in diameter and seventeen inches long. The antenna elements-13 and I4 were also one inch in" diameter and-the longer arm I3 was seven and a half inches long neeting'the'elements I3a'nd I4 of the antenna member II tothe transmission line members I8 and I9. .The shorter member I4 may be con; nected directly to the'outer conductor I9 in any desired, fashion,v as by welding, for example; Means is provided for passingthe longer element I3 through an opening in the outer conductor I 9 intcr engagement with theinner' conductor I 8 and 2 than 2, benefit was obtained by tilting the dip leg The amount of tilt of the dipole has an impm found to be accountable for approximately 2 3, and the arrangement of the antenna membei II wasresponsible for the remaining 2. 'If the arms I3 and I4 were of equal length," 'slightly'l" s tant 'eifect on the "beam shift. Thus if -the difiol is at right angles with respect to the axis of the paraboloid reflector there is no shifting of the beam. As the tilt is increased the beam shift is increased, but inasmuch as the mechanical force tending to cause whipping of the rotating parts increases rapidly as the angle of tilt increases, there are mechanical limitations to the amount of tilting permissible.

The reflector may comprise any desired reflecting surface. However, in order to minimize wind pressures on the reflector, it is preferable to form the paraboloid reflector in the form of a mesh, as by means of wires or rods as, for example, a plurality of concentric rings connected to radially extending members as shown in Figs. 1 and 2. In the above specific example the spacing between the members was approximately four inches.

While I have shown and described a particular embodiment of my invention, it will be obvious to those skilled in the art that changes and modifications may be made without departing from my invention in its broader aspects, and I therefore aim in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In an antenna system comprising a reflector the beam radiated from said antenna member is at anangle with respect to said axis, means for exciting said antenna member, and means for rotating said antenna member on said axis with respect to said reflector. i I

2. In a beam antenna system comprising a reflector having a directive axis, a directive array located on the axis of said reflector, said array comprising a linear radiator located at substantially the focus of said reflector and a reflector member also located on the axis of said reflector and arranged to reflect radiation from said radiator back to said reflector, said radiator extending transversely across said axis at an angle other than 90 thereto, means for exciting said radiator, whereby the beam radiated from said radiator is at an acute angle with respect to said axis, and means for rotating said array on said axis with respect to the reflector.

3. In a beam antenna system comprising a reflector having a directive axis, a directive array located on the axis of said reflector, said array comprising a linear radiator member located at the focus of said reflector, and a reflector member also located on the axis of said reflector and arranged to reflect radiation from said radiator back to said reflector, and means for exciting said radiator, said radiator member being positioned transversely at an angle other than 90 with respect to said axis whereby the beam radiated from said radiator is at an acute angle with respect to said axis, and means for rotating both members of said array on said axis with respect to the reflector.

4. In a beam antenna system comprising a reflector having the shape of a surface of revolution, a directive array located on the axis of said reflector and comprising a linear dipole located substantially at the focus of said reflector and areflector member arranged to reflect radiation back to said reflector, said dipole extending transversely across said axis at an angle other than thereto, means for exciting said radiator comprising concentric conductors, the inner of said conductors extending beyond the end of the outer of said conductors, said reflector member being attached to the outer end of said inner member, the elements of said dipole being connected at their inner ends to the outer end of said outer conductor and to said inner conductor, respectively, a source of signal energy, a transmission line joining said conductors and said source, and means for rotating said conductors and said array with respect to said axis.

5. In an antenna system comprising a reflector having the shape of a surface of revolution, a directive array located on the axis of said reflector and comprising a linear dipole located with its center substantially at the focus of said reflector and a reflector member arranged to reflect radiation back to said reflector, said dipole extending transversely across said axis at an angle other than 90 thereto, means for exciting said dipole consisting of only two concentrically disposed electrically conductive members, the inner of said conductors extending beyond the end of the outer of said conductors, said reflector member being attached to the outer end of said inner member, the elements of said dipole being connected at their inner ends to the outer end of said outer conductor and to said inner conductor, respectively, a source of signal energy, a transmission line joining said, conductors and said source, and means for rotating said conductors and said members with respect to said axis.

6. An antenna system comprising a, paraboloid, a linear directive radiator located on the axis of said paraboloid at substantially the focus thereof, said radiator comprising a dipole tilted at an angle other than 90 with respect to said axis, having an electrical length of approximately onehalf wave length and having axially aligned spaced-apart elements of different lengths lying on opposite sides of said axis, a reflector member having an electrical length of approximately onehalf wave arranged to reflect radiation from the dipole back to the paraboloid, the centers of said members being spaced apart approximately onequarter wave length, means for exciting said radiator member, and means for rotating said members on said axis with respect to said paraboloid.

7. A directive antenna system comprising a reflector having the shape of a surface of revolution, a linear dipole antenna located on the axis of said reflector at substantially the focus thereof, said dipole having two axially aligned elements lying on opposite sides of said axis and tilted at an angleother than 90 thereto, and means for exciting said dipole, said elements being of different lengths, whereby the currents in said elements when said dipole is energized are unbalanced and the beam radiated from antenna system is at an angle with respect to said axis.

BURTON P. BROWN, JR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,923,916' Darbord Aug. 22, 1933 2,083,242 Runge June 8, 1937 2,112,282 Fritz Mar. 29, 1938 

